Hairloss is not a story of only reduced circulation per se, however several studies show that it plays a significant contributing role in Androgenetic alopecia. DHT and insulin resistance are both associated with the microvascular insufficiency that result in the progressive minaturization of the hair follicle.
Fortunately this process can be countered by both topical and systemic means.
The topical application of the Pyridine-N-Oxides and Arginine, (both present in Dr. Proctor’s Advanced Hair Regrowth Formula) induce local vasorelaxation, and increase levels of EDRF’s (endothelium relaxing factors),resulting in a local increase and maintenance of blood flow. The systemic ingestion of Ginkgo Biloba, Grape Seed , and Bilberry extracts have been shown to increase and maintain peripheral microcapillary circulation, ultimately improving or maintaining hair growth. Following are samples of the studies identifying these mechanisms.

1: Med Hypotheses 2002 Apr;58(4):261-3

Hormone-induced aberrations in electromagnetic adhesion signaling as a developmental factor of androgenetic alopecia.

Matilainen VA, Keinanen-Kiukaanniemi SM.

Department of Public Health Science and General Practice, University of Oulu, Finland.In androgenetic alopecia, overactivation of the androgen hormone cascade in genetically predisposed persons leads to miniaturization of the dermal papilla of the hair follicle and to reduction in the number of papilla cells in the scalp, but the mechanisms explaining this miniaturization have remained unclear. According to our hypothesis, the increase of dihydrotestosterone (DHT) production in the overactive androgen state inhibits cell mitosis in the dermal papilla and contributes to the induction of programmed cell death (apoptosis). Normally, DNA molecules have a negative charge, which doubles in every cell mitosis. In the catagen and telogen phases, the sulphur-rich hair moves upwards, dehydrates and develops an increasing positive charge. In a normal hair-growth cycle, the epithelial column shortens and the secondary germ is formed and it invaginates the dermal papilla by electromagnetic attraction. In the mitotic inhibition state induced by DHT, the negative charge decreases, leading to a weakening of the electromagnetic adhesion forces and weaker electrical attraction between the undifferentiated germ cells and the dermal papilla. Insulin resistance has an additional pathogenic role in the excessive miniaturization of the hair follicle. The vasoactive substances associated with endothelial dysfunction in insulin resistance induce microcirculatory disturbance, perifollicular vasoconstriction and stimulation of smooth muscle cell proliferation in the vascular wall. This leads to microvascular insufficiency and local tissue hypoxia and progressive miniaturization of hair follicles.

1: Plast Reconstr Surg 1996 May;97(6)1109-16; discussion 1117

Transcutaneous PO2 of the scalp in male pattern baldness: a new piece to the puzzle.

Goldman BE, Fisher DM, Ringler SL.

Department of Plastic Surgery, Butterworth Hospital, Grand Rapids, Mich., USA.

Our study was designed to measure the transcutaneous PO2 of the scalp to determine if there was a relative microvascular insufficiency and associated tissue hypoxia in areas of hair loss in male pattern baldness. A controlled prospective study was performed at Butterworth Hospital, Grand Rapids, Michigan. Eighteen nonsmoking male volunteers aged 18 years and older were studied. Nine men had male pattern baldness (Juri degree II or III), and nine were controls (no male pattern baldness). Scalp temperature and transcutaneous PO2 were obtained at frontal and temporal sites in each subject. Peripheral circulation was assessed from postocclusive transcutaneous PO2 recovery time by means of maximum initial slope measurements. Statistical significance was assessed at p < 0.05. There was no significant difference in scalp temperature between male pattern baldness subjects and controls. Temporal scalp blood flow was significantly higher than frontal scalp blood flow in male pattern baldness subjects; however, there was no significant difference in controls. Transcutaneous PO2 was significantly lower in bald frontal scalp (32.2 +/- 2.0 mmHg) than in hair-bearing temporal scalp (51.8 +/- 4.4 mmHg) in men with male pattern baldness. In controls, there was no significant difference in transcutaneous PO2 of frontal scalp (53.9 +/- 3.5 mmHg) and temporal scalp (61.4 +/- 2.7 mmHg). Transcutaneous PO2 also was significantly lower in the frontal scalp of male pattern baldness subjects (32.2 +/- 2.0 mmHg) than in either frontal or temporal scalp of controls (53.9 +/- 3.5 mmHg and 61.4 +/- 2.7 mmHg, respectively). There is a relative microvascular insufficiency to regions of the scalp that lose hair in male pattern baldness. We have identified a previously unreported tissue hypoxia in bald scalp compared with hair-bearing scalp.

1: Ckin Hemorheol Microcirc 2002;23(2-4):133-8

The therapeutic effect of Ginkgo biloba extract in SHR rats and its possible mechanisms based on cerebral microvascular flow and vasomotion.

Zhang J, Fu S, Liu S, Mao T, Xiu R.

Institute of Microcirculation, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing.

This paper aimed to investigate the therapeutic effect of an extract of Ginkgo biloba leaves (EGb 761) on hypertension and its possible mechanisms in the view of cerebral microcirculation. Twenty normotensive rats and 24 SHR rats were used. Surgical preparation was made to produce a cranial window for observation of the capillary network on the cerebral cortex. The intravital videomicroscopy equipped with digital image processing system and laser Doppler flowmeter were used for this study. The arterial blood pressure, red cell velocity (V), microvacular diameter (D), number of open capillaries (OCN), circulating endothelial cells (CEC) in blood, relative blood flow (Flow) and frequency (Fc), amplitude (AMP) of vasomotion were measured. The obtained data were compared between EGb-treated rats that received per os 100 mg/kg/d for 9 days and placebo control rats. Untreated SHR rats showed very severe dysfunction in the microcirculation with high blood pressure (213 +/- 16.7 mmHg). The blood pressure decreased significantly to 153 +/- 20 mmHg in EGb-treated SHRs group, compared with those of untreated rats (p < 0.01). Both normotensive and hypertensive rats increased the blood flow velocity and LDF flow after EGb-treatment. The vasomotion property, the CEC and OCN changed greatly in EGb-treated SHR rats, but no significant difference was observed in normotensive rats. It was suggested that EGb 761 had therapeutic effect on SHR rats by increasing blood perfusion, regulating vasomotion function, opening efficiently capillaries and releasing the peripheral resistance. The injured vascular endothelium of SHR rats was also partly reversed by EGb-treatment. It was concluded that EGb 761 could be used to regulate hypertension and to protect the cerebral microcirculatory function.